This invention pertains to a method for chemically texturing a landing zone on a substrate used to manufacture a magnetic disk.
FIG. 1 illustrates a typical prior art disk drive 1 comprising a magnetic disk 2 and a read-write head 3. Disk 2 is coupled to a motor 4 for rotating disk 2. Read-write head 3 is mounted on a suspension 5. When disk 2 rotates, an air bearing forms above disk 2, and read-write head 3 xe2x80x9cfliesxe2x80x9d above magnetic disk 2. When disk drive 1 is turned off, read-write head 3 is positioned over a portion of disk 2 called the contact-start-stop, or xe2x80x9cCSSxe2x80x9d zone 2a. Concurrently, rotation of disk 2 slows, until it finally comes to a stop. When this happens, read-write head 3 comes into contact with disk 2 at CSS zone 2a. When disk drive 1 is turned on, disk 2 begins rotating. Eventually, the rotational velocity of disk 2 is sufficient to form an air bearing, thereby enabling head 3 to fly on that air bearing.
When disk 2 first begins rotating, head 3 drags along the surface of disk 2. Accordingly, steps must be taken to reduce or minimize static friction (xe2x80x9cstictionxe2x80x9d) between disk 2 and head 3. One way of doing this is by providing a texture in CSS zone 2a. For disks using NiP-plated aluminum substrates, it has been suggested that a laser can be used to form texture bumps in the CSS zone. See, for example, U.S. Pat. No. 5,062,021, issued to Ranjan.
Ranjan is directed toward texturing a NiP-plated aluminum substrate. It is also known in the art that one can manufacture magnetic disks using glass substrates. (Glass has certain advantages over NiP-plated aluminum substrates, e.g. superior hardness and shock resistance.) It has also been suggested that one can form laser texture bumps on a glass substrate. See, for example, Kuo, et al., xe2x80x9cLaser Zone Texturing on Glass and Glass-Ceramic Substratesxe2x80x9d, IEEE Trans. Magn. Vol. 33, No. 1, p. 944 et seq., which teaches that one can form bumps on a glass substrate to reduce stiction between the magnetic disk and a read-write head. Kuo indicates that when laser pulses from a CO2 laser are applied to a glass substrate, the volume of the glass where the laser pulse strikes the glass expands, thereby forming a laser texture bump.
Magnetic disk drive manufacturers have been striving to provide higher recording densities in magnetic recording media. In order to achieve higher recording densities, manufacturers have had to use lower flying heights. (The flying height is the distance between read-write head 3 and a magnetic recording layer within magnetic disk 2.) Trying to reduce the flying height often means having to reduce the size of the texture bumps on the disk. However, by reducing the size of the texture bumps, stiction increases. Thus, there is a tradeoff between the flying height and the stiction between the head and the disk. What is needed is a way to reduce the flying height of the read-write head without increasing stiction.
A method in accordance with the invention comprises the steps of applying a laser beam to a glass or glass-ceramic substrate, and applying an etchant to the substrate. In one embodiment, the etchant is acidic, and includes fluorine, e.g. fluoride ions. The portion of the substrate exposed to the laser beam etches much more rapidly than the portion of the substrate that is not exposed to the laser beam. Thus, any bump or ridge formed by the laser beam is etched away, resulting in a texture depression, or a texture valley. Of importance, this texture depression or valley reduces stiction without requiring one to sacrifice flying height.
After texturing, one or more underlayers, one or more magnetic layers and a protective overcoat are deposited on the substrate. The underlayer can be a material such as Cr, a Cr alloy, NiP, NiAl or other material.
A method in accordance with the invention can also be used to form servo marks on a disk. This is accomplished by exposing a portion of a substrate to a laser beam, etching the laser beam to form a depression, and depositing a magnetic film on the substrate. In one embodiment, the depression is of sufficient depth such that when a read-write head is positioned over the depression, it can detect the lack of a signal from the magnetic disk. (This lack of a signal is caused by the increased distance between the magnetic film and the read-write head, which in turn is caused by the presence of the depression.) The position of the depression is used as a servo mark.